Carbon-pile controllers with built-in snap action switch



July l5, 1958 R.,ul`-I1APPE 2,843,710

CARBON-PILE 4c:ox-r.vRoLL.ERs WITH BUILT-IN SNAP ACTION SWITCH y Filed March 23, 1954' f 2 sheets-sheet 1 'was n f* Q.,

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IN1/Emol@ Reyno/d Hoppe BY WITNESS y I W /IE 7% 'ATTORNEY July 15, 1958A R. HAPPE 2,843,710

CARBON-PILE CONTROLLERS WITH BUILT-IN SNAP ACTION SWITCH Filed March 23. 1954 2 Sheets-Sheet 2 I INVENToR. Reyno/d Happe BY WlTNESS 7W ATTORNEY United States Patent CARBONPILE CONTROLLERS WITH BUILT-IN SNAP ACTION SWITCH Reynold Happe, Princeton, N. J., assigner to The Singer Manufacturing Company, Elizabeth, N. J., a corpora tion of New Jersey Application March 23, 1954, Serial No. 418,065

1 Claim. (Cl. Mil-51) rThis invention relates to carbon-pile rheostats or controllers `and more specifically to lmanually-operated controllers of the adjustable resistance type for controlling the speed of the motors used for driving sewing machines.

`In conventional controllers as presently manufactured and represented 'by the type shown and described in the U. S. Patent No. 2,l l7,257, May 10, 1938, C. R. Schenk, the closing and opening of the controller circuit is made through the contacts between a weak bow-spring and the s-omewhat loose pressure heads -at the tops of the carbon piles. This rather unstable condition gives rise to much arcing during the initial closing and opening periods and produces annoying interference with radio and television reception.

It is an object of this invention, therefore, to provide a carbon-pile controller which shall be substantially free of the random arcing which causes radio-frequency int-erference.

According to this invention, this desirable result is accomplished by using a snap-action switch operatively connected with the controller actuator to take over the circuit-opening and circuit-closing function of the controller, the bridging bow-spring always remaining in Contact with the pressure heads in a stable pressure relation therewith. The substitution of the snap-action switch with its precise and positive action for the unstable and somewhat random-acting contacts of the conventional controller results in a substantial reduction in the arcing incident to circuit closing and opening.

With 'the above and other objects in View, as will hereinafter appear, the invention comprises the devices, combinations and arrangements of parts hereinafter set forth and illustrated in the accompanying drawings of a preferred embodiment of the invention, from which the several features of the invention and the advantages attained thereby, will be readily understood by those skilled in the art.

In the accompanying drawings,

Fig. l is a longitudinal vertical section, through a rheostat embodying the invention. t

`Fig. 2 is a top plan view of the rheostat of Fig. l taken with the cover removed.

Fig. 3 is a transverse section taken on `the line 3-3 of Fig. l.

Fig. 4 is a bottom plan detail view showing the switch parts.

Fig. 5 isa fragmentary side elevation view taken in the direction of the arrows 5-5 of Fig. 3.

Fig. 6 is a fragmentary side elevation View taken in the direction of the arrows 6 6 of Fig. 3.

Fig. 7 is a detail View, partly in section, showing a contact support.

Fig. 8 is a schematic diagram showing the electrical circuit of the rheostat.

Referring now to Figjl, there is shown a rheostat adapted Vto be placed on the yfloor and operated by foot, and `quite similar t-o the rheostat shown and described in the U. S. Patent No. 2,117,257, May 10, 1938, C. R.

2,843,71@ patented July 15, 1958 Schenk, `and to which reference may be had for an understanding of that part of the construction thereof which is not part of this invention.

A casing for the rheostat comprises a hollow top or cover member itl and a bottom or base member 11, each of which is molded in one piece from phenolic condensation material or from artificial resin.

Mounted on the base member lll by means of screws 12--12 is the usual carbon compression type rheostat unit 13 which comprises a porcelain body 14 having spaced, parallel Wells 15-15 housing stacks or piles 16 of carbon discs, which piles are each connected at one end to `a terminal screw 17 and at the other end to a conducting pressure head 13. The pressure heads 1S are bridged by a weak, conducting bow-spring 19 carried by an operating pull-rod 2@ which also carries a stiffer backing spring 21. The pull-rod 2i) is surrounded by a coiled recovery spring 22 which biases the parts to the positions shown, in which the spring i9 bridges the pressure heads 1S and an adjustable stop member 23 contacts an exterior wall 24 of the porcelain body 14. A nut 25, secured to the stop member 23, is `threaded onto the pullrod Ztl and may be manipulated to vadjust the pressure exerted on the carbon piles 16 by the bow-spring 19 to set the initial or maximum resistance of the rheostat to a desired value.

The pull-rod 2@ has screwed into its lfree end an adjusting nut 26 which is engaged by a strap 27 pivotally connected at 28 to a lever 29 fulcrumed at 30 on the ears 3l of a plate 32 screwed to the base 11. The lever 29 has an operating arm 3.3 which carries a cross-bar 3ft to the ends of which are connected tensioned recovery springs .3E- 35 anchored to notched horns 36-36 rising from the plate 32.

The cover l@ is formed with a rectangular, vertical guideway 37 in which is fitted ya pedal slide 38 which is formed to straddle the arm 33 and has, at its lower end, faces 39 resting on the bar 34.

The above describes a conventional carbon-pile rheostat, and lthere will now be described 'additional struc- 'ture in the form of a snap-action switch with special coaction with the rheostat for substantially eliminating `the radio-frequency interference caused by random arcing. The switch is of the same type and configuration as that shown and described in the applicants copending application Serial No. 357,518, filed May 26, 1953, now U. S. Patent No. 2,789,172, and reference may be had to this application for a more complete explanation of its operation.

As seen best in Figs. 3 and 4, the switch parts are hung beneath the porcelain body le by special brackets secured by the terminal screws 17-1'7. A rst bracket dit, secured to the body 14 by the left-hand terminal screw 17, as viewed in Fig. 3, is formed with a bent-over top portion il (Fig. 6) into which is threaded a 'terminal screw 42 for connecting the insulated line lead 43. The 'bottom portion of the bracket dii is formed with a bentback portion 44 to which is secured, by means of a rivet 45, insulating blocks or spacers 46, 47 which support a contact bracket 4S insulated therefrom, as seen best in Fig. 7. The bracket 48 is tapped to receive a terminal screw i9 for connecting the insulated line lead 56, and is bent to terminate at its free end in a contact 51 facing and spaced from the insulating 'block 46. As will be seen, the contact 51 forms a stationary switch contact and the block`46 serves as a stop for the movable switch contract.

A second bracket 52, secured to the porcelain body 14 by the rightehand terminal screw 17, as viewed in Fig. 3, is formed with a bent-over portion 53 having an !shape terminating in a tuinedtlown portion 54 which serves as a limit stop for the switch as will be described presently.

A post 55 is secured to the L-shaped portion 53 and serves as the sole support for a eXible band of hat spring material comprising spaced-apart limbs 56 and 57, The band is bent around the post 55 and is secured thereto by means of a screw 5%, A straight link 59 is held in compression between the free ends `of the limbs 56 land 57 as seen best in Fig. 4. The limb 5e terminates in a sharplybent portion 60 which carries a contact di, which, together with the contact S1, form means for opening or closing a circuit through the switch.

The adjustable stop member 2,3 is formed with a depending portion dZ, Fig. 1, which carries an insulated button 63 adapted to bear against the switch limb or to be retracted `therefrom accordingly as the pull-rod is operated to increase or to decrease the resistance of the piles 115 responsive to manipulation of the pedal slide 35.

Reference to Fig. 8 will make clear the operation of ythis device. cates the rest or non-operated condition of the controller. it will be seen that, in this position, the contacts and 61 are open and the spring 19 exerts a minimum pressure `on the piles 16. The button 63 in this position acting on the switch limb 57 biases the switch to `the off or open position indicated by the solid lines, although the switch per se is normally biased to a closed position yas indi- `cated by the dotted lines and as soon as the pressure of the button 63 against the limb 57 is removed by movement of the pull-rod 20 the switch snaps to its normally closed `or on position, initial downward movement of the pedal slide .3S increases slightly the pressure exerted on the piles, and through the pull-rod Z@ and insulated button `63, the switch parts are moved with snap action to a closed position indicated by the dotted lines in Fig. 8. This sets the low speed condition for the controller', and it is to be noted that the bridging spring 19 is now in firm engagement with the pressure heads thus eliminating the loose, unstable condition which formerly gave rise to arcing with its 4attendant radio-frequency in- "e terference. `Further downward movement of the pedal slide 3S to decrease the resistance of the piles 1d, causes the insulated button 63 to move completely out o1 engagement with the limb 57, and leaves the switch in its on position, said 'limb 57 being prevented from follow The solid line position of the switc'h indi- A ing the button 63 by the stop 54. The remainder of the `control-ler movement to decrease resistance is the same as described in the U. S. Patent No. 2,117,257 indicated above, including the nal short circuiting `of the piles 16 by the element 23 bridging the fingers 64-64 which nal position sets the minimum resistance or high speed condition for the controller. Releasing the slide pedal, of course, causes these events to occur in inverse chronological order nally leaving the switch in a biased open position due to the resting pressure of the button 63 on the limb 57.

it will be observed that the structure described above provides a snap-action switch combined with a carbon pile controller in which a casing for the switch is dispensed with, and the switch parts are protectively positioned between the porcelain body of the rheostat unit and the insulation of the base member and requires no increase in the over-all dimensions of the conventional unit of the U. S. Patent No. 2,117,257, which latter unit does not contain a snap-action switch.

Having thus set forth the nature of the invention, what 1 claim herein is:

The combination with a carbon compression rheostat Khaving terminals for external connection and including a carbon compression resistor, an operating pull-rod and spring means controlled by said pull-rod to apply vari-- able operative pressure to said resistor, of a snap-action switch norm-ally biased per se to a closed-circuit position, connected electrically in series wit'h said resistor and said terminals and connected mechanically to said pull-rod to be biased to an open-circuit posit-ion for an initial range of pressure-increasing movement of said pull-rod and disconnected from said pull-rod for movement thereof beyond said range.

References Cited in the tile of this patent UNTTED STATES PATENTS 774,460 Waddell Nov. 8, 190Ar 1,777,988 Wilms Oct. 7, 1930 2,117,257 Schenk May 10, 1938 2,371,772 Nani Mar. 20, 1945 2,533,519 Sharenow Dec. 12, 1950 FOREEGN PATENTS 501,738 Germany June 19, 1930 

